Interpretive Summary: This contribution will form a section of The Jepson Manual of the higher plants of California, a manual published by the University of California to provide up-to date information on the taxonomy, distribution, and ecological status of all plants that are wild or invasive in California, together with a guide for identification, aimed at professional and sophisticated amateur users. The taxonomy, distribution, and ecological status of all species of Acer (maples) that are wild or subject to escape in California is reevaluated, based primarily on a thorough reexamination of available herbarium specimens, and a guide for identification is supplied. In addition, the family boundaries are realigned to bring Acer and Aesculus (buckeyes) into the family Sapindaceae, in line with recent work in several laboratories. Six species in the genus Acer are included. Several species are mildly invasive, and the whole genus is very important in cultivation (as ornamentals) and in forestry (as dominant trees in many habitats). This contribution provides up-to-date information on the biology of this group of species, along with identification aids. It will support accurate identification of species of economic importance as ornamentals forest trees. It will be used by professional land managers, educators, conservationists, and sophisticated amateur botanists and horticulturalists, insuring that work on land management and conservation will be based on full, accurate and up-to-date information about the basic biology and relationships of these organisms.

Technical Abstract:
The genus Acer (maples) is treated for The Jepson Manual of the higher plants of California, a detailed floristic manual for the state published by the University of California. Six species are recognized; full morphological descriptions, dichotomous keys, and brief summaries of geographical and ecological distribution, economic use, and taxonomic notes are given for each of them, and family boundaries are realigned to bring Acer and Aesculus (buckeyes) into the family Sapindaceae, in line with recent work in several laboratories. These species are important in cultivation (as ornamentals) and in forestry (as dominant trees in many habitats). This contribution will support accurate identification of species of economic importance as ornamentals forest trees.